Photocathode, electron tube, and method of assembling photocathode

Abstract

The invention relates to a photocathode and the like having such structure for holding a photocathode plate on a light transparent member with good reliability and workability. In the photocathode, claw portions of a holding member fixed to the light transparent member is pressed against the lower surface of a supporting plate so that a photocathode plate is sandwiched between the light transparent member and the supporting plate. Thus, the supporting plate is pressed against the photocathode plate, so that the photocathode plate is pressed against the light transparent plate by the supporting plate. This allows the photocathode plate to be held reliably by the light transparent member. This simple configuration further provides good workability in assembling.

1. A photocathode comprising:
 a light transparent member having a first surface incident with light with a predetermined wavelength, and a second surface opposing the first surface and emitting the light; 
 a photocathode plate arranged at the second surface side of said light transparent member, said photocathode plate receiving the light passing through said light transparent member and emitting photoelectrons in response to incidence of light; 
 a holding member attached to the second surface of said light transparent member and having a first opening portion in which said photocathode plate is disposed; and 
 a supporting plate arranged so as to sandwich said photocathode plate together with the second surface of said light transparent member and having a second opening portion for exposing a part of said photocathode plate so as to allow the photoelectrons from said photocathode plate to pass therethrough, 
 wherein said holding member has a fixing structure folded so as to be pressed against said supporting plate in order to press said supporting plate against said photocathode plate. 
 
   
   
     2. A photocathode according to  claim 1 , wherein the fixing structure of said holding member comprises a plurality of claw portions, said claw portions arranged on said holding member so as to surround said supporting plate at even intervals. 
   
   
     3. A photocathode according to  claim 1 , wherein said photocathode plate is fitted within said first opening portion of said holding member. 
   
   
     4. A photocathode according to  claim 1 , wherein said holding member has an annular encircling portion for encircling said photocathode plate, so that said supporting plate is fitted within said encircling portion. 
   
   
     5. A photocathode according to  claim 1 , further comprising a first conductive film electrically connected to said photocathode plate, said first conductive film being provided on the second surface of said light transparent member, so that a voltage is applied to said photocathode plate through said first conductive film. 
   
   
     6. A photocathode according to  claim 5 , wherein said holding member is composed of a conductive material and is electrically connected to said first conductive film, so that a voltage is applied to said photocathode plate through said holding member and said first conductive film. 
   
   
     7. A photocathode according to  claim 1 , wherein a bias voltage is applied between both surfaces of said photocathode plate. 
   
   
     8. A photocathode according to  claim 7 , further comprising a second conductive film electrically connected to said photocathode plate, said second conductive film being provided on said supporting plate so as to continue from one surface of said supporting plate contacting with said photocathode plate to the other surface of said supporting plate opposing the one surface via a wall surface of said supporting plate defining said second opening portion, so that a voltage is applied to said photocathode plate through said second conductive film. 
   
   
     9. An electron tube including a photocathode according to  claim 1 .